A silica-based coating film has superior heat resistance, abrasion resistance, and corrosion resistance. Therefore, such a silica-based coating film has been widely used as a film for protecting the surface of molded products made of various synthesized resins, or glass.
As a method for forming the silica-based coating film, various methods are known. However, in general, a sol-gel method has been widely used. The sol-gel method is a method in which alkoxysilane is dissolved in an organic solvent containing mainly alcohol, and the alkoxysilane is hydrolyzed and condensed to prepare a coating solution containing a silica sol composition, then the obtained coating solution is coated on the surface of the molded product, and subjected to a heat treatment to form a silica-based coating film.
On the other hand, it is required to provide functions in accordance with the intended use of the coating film on the surface of molded products made of various synthesized resins, or glass. Therefore, various silica-based coating films having various functions have been developed. For example, in order to provide an antibacterial inorganic coating film having antibacterial activity for a long period of time, a silica-based coating film is suggested in which an antibacterial agent, such as silver, copper, and titanium oxide, is added to an inorganic coating solution containing a silica dispersion oligomer solution (Patent Document No. 1).
In addition, a silica-based coating film, which can prevent the surface of the molded product from being charged, is desired, and the development of a silica sol composition having conductivity is desired.